Due to their superparamagnetism property as well as the high surface-to-volume ratios, magnetic nanomaterials (MNMs) have been utilized as both sorbents and sensors in analytical chemistry. Different aspects of the application of MNMs in analytical chemistry have widely been reviewed. However, the application of MNMs in the magnetic field sensors has been less investigated. Magnetic field sensors can be generally divided into two categories: magnetoresistive sensors and nonmagnetoresistive sensors. Magnetoresistive sensors rely on the dependence of material resistance to its magnetization state. The nonmagnetoresistive sensors can be utilized under high magnetic fields without being bothered by magnetic saturation. This chapter provides an overview of the application of MNMs in magnetic field sensors along with fundamental principles.
